The effect of ligation on the loadÒdeflection characteristics of nickelÒtitanium orthodontic wire
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The effect of ligation on the loadÒdeflection characteristics of nickelÒtitanium orthodontic wire
The European Journal of Orthodontics 2007 29(6):578-582; doi:10.1093/ejo/cjm068
Shugo Kasuya*, Satoshi Nagasaka*, Ai Hanyuda*, Sadao Ishimura** and Ayao Hirashita*
* Department of Orthodontic, Tsurumi University School of Dental Medicine, Yokohama, Japan
** Laboratory of Mathematics, Tsurumi University School of Dental Medicine, Yokohama, Japan
Abstract
This study examined the effect of ligation on the loadÒdeflection characteristics of nickelÒtitanium (NiTi) orthodontic wire. A modified three-point bending system was used for bending the NiTi round wire, which was inserted and ligated in the slots of three brackets, one of which was bonded to each of the three bender rods. Three different ligation methods, stainless steel ligature (SSL), slot lid (SL), and elastomeric ligature (EL), were employed, as well as a control with neither bracket nor ligation (NBL). The tests were repeated five times under each condition. Comparisons were made of loadÒdeflection curve, load at maximum deflection of 2000 µm, and load at a deflection of 1500 µm during unloading. Analysis of Variance (ANOVA) and Dunnett's test were conducted to determine method difference ( = 0.05). The interaction between deflection and ligation was tested, using repeated-measures ANOVA ( = 0.05).
The load values of the ligation groups were two to three times greater than the NBL group at a deflection of 1500 µm during unloading: 4.37 N for EL, 3.90 N for SSL, 3.02 N for SL, and 1.49 N for NBL (P < 0.01). For the EL, a plateau region disappeared in the unloading curve. SL showed the smallest load. The ligation of the bracket wire may make NiTi wire exhibit a significantly heavier load than that traditionally expected. NiTi wire exhibited the majority of its true superelasticity with SL, whereas EL may act as a restraint on its superelasticity.
Address for correspondence Shugo Kasuya, Department of Orthodontics, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama, Japan E-mail: kasuya-shugo@tsurumi-u.ac.jp
Copyright © 2007 European Orthodontic Society
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